Compressor and Power Transmission Device

ABSTRACT

A compressor of the present invention having an electromagnetic clutch ( 14 ) for transmitting a driving force from a driving source ( 15 ) to a rotary shaft ( 4 ), in which the clutch ( 14 ) includes a rotor ( 16 ) rotated by receiving the driving force of the driving source ( 15 ), the rotor ( 16 ) containing an electromagnetic solenoid ( 22 ), a hub ( 48 ) fixed to the rotary shaft ( 4 ), and a clutch mechanism ( 24 ) capable of connecting the rotor ( 16 ) and the hub ( 48 ) to each other; the clutch mechanism ( 24 ) has an armature ( 26 ) attracted to the rotor ( 16 ) when the solenoid ( 22 ) is in an operating state, an inner support ( 31 ) coupled to the hub ( 48 ), and a shim ( 62 ) sandwiched between the inner support ( 31 ) and the hub ( 48 ); and the shim ( 62 ) determines the size of a gap (L) to be secured between the rotor ( 16 ) and the armature ( 26 ) when the solenoid ( 22 ) is in a resting state.

TECHNICAL FIELD

The present invention relates to a compressor and a power transmissiondevice which are suitable for a refrigeration device using CO₂ gas asrefrigerant.

BACKGROUND ART

A compressor of this type has a housing, which contains a compressionunit. The compression unit carries out a sequence of processes, startingwith suction of refrigerant, followed by compression and discharge ofthe refrigerant.

The compression unit is connected to a rotary shaft which drives thecompression unit. The rotary shaft is disposed within the housing, andboth end portions of the rotary shaft are rotatably supported by thehousing through bearings. The rotary shaft has one end that isprotruding from the housing. This one end is connected to a drivingsource through a power transmission path. Therefore, when the drivingforce of the driving source is transmitted through the powertransmission path to the rotary shaft, the rotary shaft is rotated, andthis rotation drives the compression unit.

For example, a power transmission device such as an electromagneticclutch is also interposed in the power transmission path. The powertransmission device controls the transmission of the driving force fromthe driving source to the compression unit.

Meanwhile, the housing is filled with the refrigerant, so that thepressure in the housing is increased while the compression unit isdriven. In order to prevent the refrigerant from leaking out of thehousing, the compressor further includes a shaft sealing unit, namely,mechanical seal, which is set in between the rotary shaft and thehousing. The mechanical seal is placed near the bearing that is locatedon the side of the one end of the rotary shaft, and seals the rotaryshaft with respect to the housing.

The mechanical seal includes a fixed seal face that surrounds the rotaryshaft and a movable seal face that rotates with the rotary shaft andslides against the fixed seal face. The mechanical seal receives highpressure in the housing on the fixed seal face. Such sealing effect ofthe mechanical seal is generally presented by the product of fluidpressure (P) applied to the fixed and movable seal faces and peripheralvelocity (V) of the movable seal face, that is, a PV value.

If CO₂ gas is used as refrigerant as mentioned above, the CO₂ gasdecreases burdens on the global environment as it has smaller globalwarming potential than chlorofluorocarbon (CFC) that is commonly used asrefrigerant. In such a case, however, the compressor is required tocompress CO₂ into a high-pressure range where the CO₂ comes into a supercritical state. For this reason, during operation of the compressor, thepressure in the housing becomes approximately seven to ten times higherthan the case in which CFC is used as refrigerant.

The above-mentioned pressure increase in the housing raises the PV valueto exceed an allowable level of the mechanical seal. The seal faces ofthe mechanical seal are then liable to be worn early. As a result, themechanical seal cannot stably confine the high-pressure CO₂ refrigerantin the housing for a long period. This produces the possibility that theCO₂ refrigerant will leak out of the housing while the compressor isused.

To prevent the leakage of the CO₂ refrigerant by using the mechanicalseal, it is necessary to decrease the PV value of the mechanical seal tothe allowable level. To this end, the peripheral velocity (V) of themovable seal face is reduced. In this case, to be more specific, thediameter of the rotary shaft may be reduced.

Meanwhile, when the power transmission device is an electromagneticclutch, this electromagnetic clutch includes a rotor located on thedriving source side and an armature located on the rotary shaft side.The rotor and the armature must be spaced away from each other with agiven gap between them when the electromagnetic clutch is in a restingstate (refer to gap α disclosed in Patent Document 1 mentioned below).

In order to secure this gap, a ring-shaped shim is utilized. The shim isplaced between the rotary shaft and the hub of the electromagneticclutch. More specifically, one end portion of the rotary shaft is formedas a small-diameter shaft portion, which provides the rotary shaft withan annular stepped face that is opposed to the hub. When placed betweenthe hub and the stepped face, the shim creates the gap between the rotorand the armature.

However, if the diameter of the rotary shaft is reduced to decrease thePV value of the mechanical seal, and moreover the one end portion of therotary shaft is formed into the small-diameter shaft portion to providethe stepped face, the rotary shaft will be deficient in mechanicalstrength at the small-diameter shaft portion, and will be incapable ofcarrying out a stable transmission of the driving force, or torquetransmission, from the driving source to the compression unit. Thismight result in a fracture of the rotary shaft.

Patent Document 1: Unexamined Japanese Patent Publication No. DISCLOSUREOF THE INVENTION

It is an object of the present invention to provide a compressor and apower transmission device which secures durability of a shaft sealingunit while avoiding the lack of strength of a rotary shaft even when CO₂is used as a working fluid.

In order to accomplish the above object, the compressor comprises ahousing; a rotary shaft rotatably supported in the housing, the rotaryshaft having one end protruding from the housing; a compression unitcontained in the housing, the compression unit for performing a sequenceof processes, starting with suction of a working fluid, followed bycompression and discharge of the working fluid, when driven by therotary shaft; a shaft sealing unit disposed between the housing and therotary shaft, for airtightly sealing the inside of the housing; and apower transmission device for transmitting a driving force from adriving source to the one end of the rotary shaft.

The power transmission device includes a rotor rotatably supported by anouter surface of the housing through a bearing, for receiving thedriving force from the driving source; a hub coupled to the one end ofthe rotary shaft, for rotating with the rotary shaft; a clutch mechanismfor controlling transmission of rotational force from the rotor to thehub, the clutch mechanism including a first rotation member disposedadjacent to the rotor in relation to an axial direction of the rotaryshaft, the first rotation member being capable of receiving therotational force of the rotor and a second rotation member disposedadjacent to the hub in relation to the axial direction, the secondrotation member being coupled to the hub and capable of receiving therotational force of the first rotation member; and a shim sandwichedbetween the second rotation member and the hub, the shim determining aposition of the first rotation member with respect to the rotor relativein the axial direction.

In the above compressor, the shim is placed not between the hub and therotary shaft but between the hub and the second rotation member.Therefore, the rotary shaft is not required to be reduced in diameterdue to the placement of the shim. The diameter of the rotary shaft canbe reduced only in consideration of use of CO₂ gas as a working fluid,so that the diameter of the rotary shaft is not undesirably reduced.This makes it possible to secure durability of a shaft-sealing unit fora long term while avoiding the lack of mechanical strength in the rotaryshaft, thereby significantly improving reliability of the compressor.

To be concrete, the power transmission device is an electromagneticclutch including an electromagnetic solenoid disposed within the rotor.In this case, the first rotation member of the clutch mechanism includesan armature for receiving the rotational force of the rotor when theelectromagnetic solenoid is in an operating state and the armature isattracted to the rotor by the electromagnetic solenoid, and a springelement for urging the armature to secure a gap between the rotor andthe armature in the axial direction, when the electromagnetic solenoidis in a resting state, the shim determining a size of the gap.

The power transmission device may be a torque limiter for breakingtransmission of the rotational force from the rotor to the rotary shaftwhen the rotary shaft comes into a locked state. In this case, the shimis used for position adjustment of the spring element and the rotor.

No matter whether the power transmission device is the electromagneticclutch or the torque limiter, the shim located between the hub and thesecond rotation member can have a larger pressure-receiving area thanthat of a shim located between the hub and the rotary shaft.Consequently, the shim is never buckled at the time of screw fasteningfor fixing the hub. Abrasion of the shim due to a tremor caused byvariable load is also reduced.

The clutch mechanism further includes a fastening element disposed ineither one of the second rotation member and the hub, and a receivingelement disposed in the other of the second rotation member and the hub,for receiving the fastening element to couple the second rotation memberand the hub to each other. In this case, the shim has a bore into whichthe fastening element is inserted. More specifically, the fasteningelement is any one of a bolt, a pin, and a protruding portion integrallyformed in one or the other of the second rotation member and the hub.

The fastening element and the receiving element easily and firmly couplethe second rotation member and the hub to each other, and are greatlyuseful for improving the productivity of the compressor.

The invention also provides the compressor using CO₂ gas as a workingfluid and the power transmission device included in the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a part of a compressor according to afirst embodiment;

FIG. 2 is a sectional exploded view showing a part of a powertransmission device of FIG. 1;

FIG. 3 is a front view of the power transmission device of FIG. 1;

FIG. 4 is a front view of a hub of FIG. 2;

FIG. 5 is a front view of a shim of FIG. 2;

FIG. 6 is a sectional view showing a part of a compressor according to asecond embodiment;

FIG. 7 is a sectional view showing a part of a compressor according to athird embodiment;

FIG. 8 is a front view of a power transmission device of FIG. 7;

FIG. 9 is a front view of a shim of FIG. 7; and

FIG. 10 is a sectional view showing a modification example of a couplingstructure for connecting an inner support and the hub of FIG. 2 to eachother.

BEST MODE OF CARRYING OUT THE INVENTION

FIG. 1 shows a part of a compressor according to a first embodiment. Thecompressor is contained in a refrigeration device using CO₂ asrefrigerant. More specifically, the refrigeration plat is included in avehicle air conditioning system.

The compressor has a housing 2. FIG. 1 only shows a part of the housing2. In the housing 2, there is disposed a rotary shaft 4, which isrotatably supported through bearings (not shown) with respect to thehousing 2.

A mechanical seal 6 serving as a shaft sealing unit is also located inthe housing 2. The mechanical seal 6 keeps an airtight condition betweenthe housing 2 and the rotary shaft 4. More specifically, the mechanicalseal 6 includes a sheet 7 a fixed to the housing 2 and a seal ring 7 bfitted to the rotary shaft 4 and pressed against the sheet 7 a. Thesheet 7 a and the seal ring 7 b have annular seal faces 8 a and 8 b thatare in close contact.

Instead of the mechanical seal 6, lip seals (not shown) may be utilizedas the shaft sealing unit. The lip seal is placed between the rotaryshaft 4 and the housing 2 and has a cylindrical seal face.

The rotary shaft 4 has one end portion 10 protruding from the housing 2and the other end portion (not shown) that is positioned within thehousing 2. The other end portion of the rotary shaft 4 is connected to acompression unit 12. The compression unit 12 is accommodated in thehousing 2 and is driven by the rotary shaft 4. Specifically, thecompression unit 12 is, for example, either one of a swash-platecompression unit including a piston that makes a reciprocating motionaccording to the rotary shaft 4 and a scroll compression unit includinga movable scroll that makes an orbiting motion according to the rotaryshaft 4.

When driven, the compression unit 12 repeatedly performs a sequence ofprocesses, starting with suction of CO₂ refrigerant, followed bycompression and discharge of the CO₂ refrigerant, thereby circulatingthe CO₂ refrigerant through a refrigerant circuit of the refrigerationdevice.

As illustrated in FIG. 1, the one end portion 10 of the rotary shaft 4is connected to a driving source 15 through a power transmission path13. The driving source 15 is either an engine or motor of a vehicle. Anelectromagnetic clutch 14 serving as a power transmission device isinterposed in the power transmission path 13. The electromagnetic clutch14 is mounted on the compressor.

More specifically, the electromagnetic clutch 14 includes a rotor 16.The rotor 16 is rotatably supported by an outer circumferential surfaceof the housing 2 through a bearing 18. The rotor 16 has an end face 16 alocated on the side of the one end portion 10 of the rotary shaft 4, andis also formed as a driving pulley 20. The driving pulley 20 isconnected to the power transmission path 13, more specifically, to anoutput pulley (not shown) of the driving source 15 through an endlessdriving belt (not shown). Accordingly, when a driving force istransmitted from the driving source 15 to the driving pulley 20, thedriving pulley 20, or the rotor 16, is rotated in one direction.

The electromagnetic clutch 14 has a clutch mechanism 24. The clutchmechanism 24 will be described below in detail.

The clutch mechanism 24 includes an electromagnetic solenoid 22 locatedin the inside of the rotor 16. The electromagnetic solenoid 22 is fixedonto the outer circumferential surface of the housing 2 through aring-shaped bracket 21.

The clutch mechanism 24 further includes a first rotation member, thatis, a disc-shaped armature 26. The armature 26 is disposed opposed tothe one end face 16 a of the rotor 16. The armature 26 has a circularopening 27 in the center thereof. As illustrated in FIG. 1, when theelectromagnetic clutch 14 is in a resting state, there is secured agiven gap amount L between the armature 26 and the one end face 16 a ofthe rotor 16.

The armature 26 is coupled to an inner support 31 serving as a secondrotation member through a spring unit 28. The spring unit 28 is set inan outer surface of the armature 26, that is, in an opposite face to therotor 16. The spring unit 28 has an outer ring 30 and a spring element32 that is interfitted in the outer ring 30. The spring element 32 ismade of synthetic rubber and formed to have a ring-like shape. As isapparent from FIG. 1, the spring element 32 integrally has a pluralityof projections 32 a in an inner circumference thereof. The projections32 a are arranged at regular intervals in a circumferential direction ofthe spring unit 28 and are in contact with the armature 26.

The outer ring 30 is made of metal and integrally has three lugs 33 inan outer circumference thereof. The lugs 33 are arranged at regularintervals in a circumferential direction of the outer ring 30, and fixedon the armature 26 by using rivets 34. The spring unit 28 is accordinglycoupled to the armature 26 in an outer circumferential portion thereof.FIG. 1 shows only one of the lugs 33 and one of the rivets 34.

The inner support 31 is made of metal and has a disc-like shape. Theinner support 31 has a rim 31 a in an outer circumference thereof. Therim 31 a bears the spring element 32 in consort with the outer ring 30so that the spring element 32 is sandwiched between the rim 31 a and theouter ring 30, and is fixed on the spring element 32. In short, theinner support 31 is coupled to the armature 26 serving as the firstrotation member with the spring unit 28 intervening therebetween.

The inner support 31 is fitted to a hub 48 in an inner circumferentialportion thereof. The hub 48 is mounted on the one end portion 10 of therotary shaft 4. More concretely, as illustrated in FIGS. 2 and 3, theinner support 31 has a circular opening 42 positioned in the centerthereof and three bores 40 arranged outside the opening 42. The bores 40are distributed on the same circle and arranged at regular intervals ina circumferential direction of the inner support 31. The inner support31 further has three bores 41. The bores 41 are arranged in thecircumferential direction of the inner support 31 so that each of thebores 41 is located between two adjacent bores 40.

It should be noted that the opening 42 and the bores 40 and 41 of theinner support 31 are disposed within an area with a smaller diameterthan that of the opening 27 of the armature 26.

As is evident from FIG. 2, the hub 48 has a shape of a stepped hollowcylinder. Formed in the hub 48 is an axial bore 49. The axial bore 49extends along an axis of the hub 48 and passes through the hub 48. Asviewed in the axial direction of the hub 48, the axial bore 49 has afemale spline 50 f in the center thereof, and one end portion of theaxial bore 49, which is located on the side of the inner support 31, isformed as a circular recessed area 51. The recessed area 51 has a largerinternal diameter than that of the axial bore 49.

A male spline 50 m is formed on the one end portion 10 of the rotaryshaft 4. The one end portion 10 has a male thread 10 a that is formed inan outer circumferential surface thereof so as to extend from the malespline 50 m to a tip end of the one end portion 10. When the one endportion 10 of the rotary shaft 4 is inserted into the axial bore 49 ofthe hub 48 from the other end side thereof, the male spline 50 m isengaged with the female spline 50 f of the axial bore 49. This allowsthe hub 48 to rotate integrally with the rotary shaft 4, relative to thecircumferential direction of the rotary shaft 4.

When the above-mentioned spline engagement is completed, the male thread10 a of the rotary shaft 4 is located within the recessed area of thehub 48. As illustrated in FIG. 1, a nut 11 is screwed on the male thread10 a, thereby interlocking the hub 48 to the rotary shaft 4.

The hub 48 has a flange 52 located in the one end side of the axial bore49. The flange 52 is protruding outward in a radial direction of the hub48. The flange 52 has an external diameter that is slightly smaller thanthe internal diameter of the opening 27 of the armature 26. Formed inthe flange 52 are three screw holes 56, which are distributed on thesame circle and arranged at regular intervals in a circumferentialdirection of the hub 48. The distribution circle of the screw holes 56has the same diameter as the distribution circle of the bores 40 of theinner support 31. Therefore, as is apparent from FIG. 2, the screw holes56 can be positioned coaxially with the respective bores 40.

Referring to FIG. 4 for more precision, three circular recesses 53 areformed in the flange 52. The circular recesses 53 correspond to therespective bores 41 of the inner support 31.

As illustrated in FIG. 2, the hub 48 further includes an annularprojection 58 in one end face thereof which is located on the flange 52side. The annular projection 58 has an external diameter slightlysmaller than an internal diameter of the opening 42 of the inner support31. Therefore, as is evident from FIG. 1, the inner support 31 is fittedon the hub 48 in a state where the annular projection 58 is inserted inthe opening 42. At this moment, the bores 40 of the inner support 31coincide with the respective screw holes 56. The annular projection 58has an internal diameter identical to an internal diameter of therecessed area 51.

At the time of the fixing of the inner support 31 to the hub 48, as isapparent from FIG. 2, a shim 62 is sandwiched between the inner support31 and the flange 52 of the hub 48. The shim 62 is used to secure thegap L.

To be more concrete, the inner support 31 and the flange 52 of the hub48 have flat receiving faces 38 and 54, respectively, with respect tothe shim 62. The shim 62 is formed into a disc and has substantially thesame external diameter as the flange 52 of the hub 48. Both sides of theshim 62 are formed as flat contact faces 64 a and 64 b to be in closecontact with the receiving faces 38 and 54, respectively.

As is obvious from FIG. 5, the shim 62 has an opening 66 located in thecenter thereof, three bores 68 arranged outside of the opening 66, andthree bores 65 each arranged between the respective two adjacent bores68. The opening 66 is allowed to coincide with the opening 42 of theinner support 31, and the bores 68 and 65 with the respective bores 40and 41 of the inner support 31.

To mount the clutch mechanism 24 on the rotary shaft 4, the hub 48 isfirstly spline-engaged with the one end portion 10 of the rotary shaft4, and the hub 48 is fixed onto the rotary shaft 4 with the nut 11.After the shim 62 is mounted on the annular projection 58 of the hub 48,the armature 26 and the inner support 31 provided with the spring unit28 are fixed to the hub 48. As a result, the shim 62 is sandwichedbetween the inner support 31 and the flange 52 of the hub 48, and thegap L is created due to thickness of the shim 62. Thereafter, as isapparent from FIG. 1, three connecting bolts 46 are screwed into therespective screw holes 56 of the flange 52 through the bores 40 and 68of the inner support 31 and the shim 62. As a result, the inner support31 is interlocked with the rotary shaft 4 with the hub 48 interveningtherebetween.

In the electromagnetic clutch 14, when the electromagnetic solenoid 22is supplied with electric power, the electromagnetic solenoid 22attracts the armature 26 while elastically deforming the spring element32 of the spring unit 28, thereby frictionally engaging the armature 26and the rotor 16 with each other. At this point, the rotation of therotor 16 is transmitted to the rotary shaft 4 through the armature 26,the spring unit 28, the inner support 31, and the hub 48. The rotaryshaft 4 then rotates together with the rotor 16 and drives thecompression unit 12.

When the electric power supply to the electromagnetic solenoid 22 isstopped, the spring element 32 of the spring unit 28 detaches thearmature 26 from the rotor 16 by using a restoring force thereof,thereby securing the gap L between the armature 26 and the rotor 16. Insuch a resting state of the electromagnetic clutch 14, accordingly, therotation of the rotor 16 is not transmitted to the rotary shaft 4, whichstops the driving of the compression unit 12.

In the compressor according to the first embodiment, the shim 62, thatsecures the given gap L between the rotor 16 and the armature 26 whenthe electromagnetic clutch 14 is in the resting state, is sandwichedbetween the inner support 31 of the clutch mechanism 24 and the hub 48.Consequently, the rotary shaft 4 does not need a stepped face formed byreducing the diameter of the rotary shaft 4 to sandwich a shim betweenthe rotary shaft 4 and the hub 48.

For that reason, when the compressor of the first embodiment uses a CO₂refrigerant, the rotary shaft 4 can be reduced in diameter regardless ofthe shim 62, and the sealing performance of the mechanical seal 6 isstably assured for a long term.

Since the shim 62 includes the large contact faces 64 a and 64 b withrespect to the inner support 31 and the hub 48, surface pressure that isapplied to the shim 62 is drastically reduced. This also decreasesabrasion of the shim 62 which is caused by vibrations of the armature26. The shim 62 then stably retains the gap L for a long period andassures a stable operation of the electromagnetic clutch 14.

Since the inner support 31 and the hub 48 are connected to each otherwith the connecting bolts 46, it is easy to achieve a firm engagementbetween the inner support 31 and the hub 48.

Compressors according to second and third embodiments will be describedbelow. Throughout the description about the compressors according to thesecond and third embodiments, members and portions identical to those ofthe compressor of the first embodiment will be referred by identicalreference marks, and descriptions thereof will be omitted. Differencesfrom the first embodiment will be explained below.

Referring to FIG. 6, the compressor according to the second embodimenthas a torque limiter 14A instead of the electromagnetic clutch 14. Thetorque limiter 14A includes a clutch mechanism 24A that connects therotor 16 and the rotary shaft 4 to each other.

The clutch mechanism 24A has a spring unit 28A as a first rotationmember. The lugs 33 of the spring unit 28A, instead of the rivets 34 ofthe first embodiment, are fixed to the rotor 16 with bolts 34A.

The spring unit 28A includes an inner ring 78 made of metal. A springelement 32 is sandwiched between the inner ring 78 and the outer ring30. The spring element 32 is interfitted both in the outer ring 30 andthe inner ring 78.

The inner support 31A is disposed in the inside of the inner ring 78.The inner support 31A is not connected to either the inner ring 78 orthe spring element 32, thereby being in a state detached from both theinner ring 78 and the spring element 32.

A boss 35 is formed in the center of an outer surface of the innersupport 31A. The boss 35 has a male screw 37 in an outer circumferentialsurface thereof. A circular recessed area 39 is formed in an innersurface of the inner support 31A. The recessed area 39 has an internaldiameter and depth that are identical to an external diameter andthickness of a flange 52A of the hub 48A. Therefore, as is evident fromFIG. 6, the inner support 31A is fitted to the hub 48A in a statereceiving the flange 52A of the hub 48A in the recessed area 39, and isfastened to the hub 48A with a plurality of connecting bolts 46.

An annular projection 58A of the hub 48A extends in an axial directionof the hub 48A and is interfitted in an opening 42 of the boss 35.Disposed between the boss 35 and the spring element 32 is a pressureplate 72. The pressure plate 72 is fastened to the boss 35 with a washer46B and a nut 46A intervening therebetween, and the nut 46A is screwedon the male thread 37 of the boss 35.

The pressure plate 72 defines an annular accommodation chamber 73 incooperation with the boss 35, the spring element 32, the inner ring 78and the inner support 31A. In other words, the accommodation chamber 73is surrounded by the above-mentioned members 31A, 32, 35 and 78. Aplurality of balls 70 are contained in the accommodation chamber 73. Theballs 70 have outer surfaces that have been subjected to hardeningtreatment, and are arranged at regular intervals in a circumferentialdirection of the inner support 31A.

The pressure plate 72 has a tapered face 72 a in an inner surface on theside of the accommodation chamber 73. The tapered face 72 a graduallyreduces width of the accommodation chamber 73 along an axial directionof the boss 35 toward the boss 35. The inner support 31A has an annularprojection 76 and an annular clearance groove 74 in the inner surface onthe side of the accommodation chamber 73. The clearance groove 74 islocated more inside than the annular projection 76, as viewed in aradial direction of the inner support 31A.

In a state shown in FIG. 6, the balls 70 are held between the taperedface 72 a of the pressure plate 72 and the annular projection 76 of theinner support 31A. The balls 70 are also in a state pressed against theinner ring 78 by an urging ring 80 such as a spiral spring. The urgingring 80 is contained in the accommodation chamber 73.

According to the second embodiment, a bottom face of the recessed area39 in the inner support 31A is formed as the flat receiving face 38. Ashim 62A is sandwiched between the receiving face 38 and a receivingface 54 of the hub 48A. The shim 62A adjusts the position of the innersupport 31A relative to the axial direction of the rotary shaft 4,secures the given gap L between the spring element 32 and the rotor 16,and prevents the spring element 32 from contacting the rotor 16.

In the compressor according to the second embodiment, when the rotor 16is supplied with the driving force and is rotated, the rotation of therotor 16 is transmitted to the hub 48A through the spring element 32,the inner ring 78, the balls 70, the annular projection 76 and the innersupport 31A, and is then transmitted from the hub 48A to the rotaryshaft 4.

During the rotation of the rotary shaft 4, when load applied to therotary shaft 4 is increased, and locking tendency or locking occurs onthe rotary shaft 4, there causes a great differential between arotational velocity of the rotor 16 and that of the rotary shaft 4. Sucha velocity differential applies great torque to the rotor 16, so thatthe balls 70 fall into the clearance groove 74 of the inner support 31Aby overcoming an urging force of the urging member 80 and frictionengagement with respect to the tapered face 72 a of the pressure plate72 and the annular projection 76 of the inner support 31A. As a result,the balls 70 fail to transmit the rotation of the rotor 16 to the innersupport 31A, which allows the torque limiter 14B to exhibit its originalfunction.

In the second embodiment, the shim 62A provides the compressor withsimilar advantages as with the shim 62 of the first embodiment.

FIGS. 7 to 9 show the compressor according to the third embodiment.

As is obvious from FIG. 7, the compressor of the third embodiment has anelectromagnetic clutch 14B. The electromagnetic clutch 14B includes,instead of the connecting bolts 46 of the first embodiment, a pluralityof hollow pins 46B for fastening an inner support 31B to a hub 48B.Therefore, as illustrated in FIG. 8, the inner support 31B has bores 44instead of the bores 40 of the first embodiment, whereas the hub 48B hasthrough holes 60 instead of the screw holes 56 of the first embodiment.A shim 62B has three bores 68B instead of the bores 68 of the firstembodiment.

The hollow pins 46B are inserted into the respective through holes 60 ofthe hub 48B through the bores 44 of the inner support 31B and the bores68B of the shim 62B, thereby fitting the inner support 31B to the hub48B.

The shim 62B of the third embodiment also exhibits similar advantages aswith the shim 62 of the first embodiment. In the case of the compressoraccording to the third embodiment, the connection of the inner support31B and the hub 48B is achieved by insertion of the hollow pins 46B.Therefore, the connection is easy, and also the radial positioning ofthe inner support 31B in relation to the hub 48B can be carried out withaccuracy. Consequently, the compressor is greatly improved inproductivity.

The hollow pins 46B are suitable for power transmission from the innersupport 31B to the hub 48B. Load, especially a shearing force, appliedto the hollow pins 46B is reduced.

FIG. 10 relates to connection of an inner support 31C and a hub 48C andshows a modification example thereof.

According to the modification example shown in FIG. 10, the innersupport 31C integrally includes protruding portions 82, and the hub 48Chas recess portions 84 in which the protruding portions 82 are inserted,respectively. Therefore, the inner support 31C and the hub 48C areconnected to each other by fitting the protruding portions 82 into therecess portions 84. In this process, the protruding portions 82penetrate bores of a shim 62C.

The protruding portions 82 and the recess portions 84 form a faucetjoint. Such a faucet joint can include the protruding portions 82 formedin the hub 48C and the recess portions 84 formed in the inner support31C.

The invention is not limited to the compressors according to the firstto fourth embodiments.

For instance, the torque limiter may be a notch type including abreak-away notch, instead of the ball type shown in FIG. 6. A notch-typetorque limiter is broken at a notch when overload is applied to thenotch, and breaks power transmission from a rotor to a rotary shaft.

1. A compressor comprising: a housing; a rotary shaft rotatablysupported in said housing, said rotary shaft having one end protrudingfrom said housing; a compression unit contained in said housing, saidcompression unit for performing a sequence of processes, starting withsuction of a working fluid, followed by compression and discharge of theworking fluid, when driven by said rotary shaft; a shaft sealing unitdisposed between said housing and said rotary shaft, for airtightlysealing the inside of said housing; and a power transmission device fortransmitting a driving force from a driving source to the one end ofsaid rotary shaft, wherein said power transmission device includes: arotor rotatably supported by an outer surface of said housing through abearing, for receiving the driving force from the driving source; a hubcoupled to the one end of said rotary shaft, for rotating with saidrotary shaft; a clutch mechanism for controlling transmission ofrotational force from the rotor to the hub, the clutch mechanismincluding a first rotation member disposed adjacent to the rotor inrelation to an axial direction of said rotary shaft, the first rotationmember being capable of receiving the rotational force of the rotor, anda second rotation member disposed adjacent to the hub in relation to theaxial direction, the second rotation member being coupled to the hub andcapable of receiving the rotational force of the first rotation member;and a shim sandwiched between the second rotation member and the hub,the shim determining a position of the first rotation member withrespect to the rotor in the axial direction.
 2. The compressor accordingto claim 1, wherein: said power transmission device is anelectromagnetic clutch including an electromagnetic solenoid disposedwithin the rotor, wherein: the first rotation member of the clutchmechanism includes: an armature for receiving the rotational force ofthe rotor when the electromagnetic solenoid is in an operating state andthe armature is attracted to the rotor by the electromagnetic solenoid,and a spring element for urging the armature to secure a gap between therotor and the armature in the axial direction when the electromagneticsolenoid is in a resting state, and wherein: the shim determines a sizeof the gap.
 3. The compressor according to claim 1, wherein: said powertransmission device is a torque limiter for breaking transmission of therotational force from the rotor to said rotary shaft when said rotaryshaft comes into a locked state, wherein: the first rotation member ofthe clutch mechanism includes a spring element connected to the rotor,and wherein: the shim secures a gap between the rotor and the springelement in the axial direction.
 4. The compressor according to claim 1,wherein: the clutch mechanism further includes a fastening elementdisposed in either one of the second rotation member and the hub, and areceiving element disposed in the other of the second rotation memberand the hub, for receiving the fastening element to couple the secondrotation member and the hub to each other, and wherein: the shim has abore into which the fastening element is inserted.
 5. The compressoraccording to claim 4, wherein: the fastening element is any one of abolt, a pin, and a protruding portion integrally formed in one or theother of the second rotation member and the hub.
 6. The compressoraccording to claim 1, wherein: the working fluid includes CO₂ gas.
 7. Apower transmission device for transmitting a driving force from adriving source to a rotary shaft, comprising: a rotor rotatably disposedso as to be coaxial with the rotary shaft, for receiving the drivingforce from the driving source; a hub coupled to the rotary shaft, forrotating with the rotary shaft; a clutch mechanism for controllingtransmission of rotational force from said rotor to said hub, saidclutch mechanism including a first rotation member disposed adjacent tosaid rotor in relation to an axial direction of the rotary shaft, thefirst rotation member being capable of receiving the rotational force ofsaid rotor, and a second rotation member disposed adjacent to said hubin relation to the axial direction, the second rotation member beingcoupled to said hub and capable of receiving rotational force of thefirst rotation member; and a shim sandwiched between the second rotationmember and said hub, said shim determining a position of the firstrotation member with respect to said rotor in the axial direction,wherein: the power transmission means is an electromagnetic clutch inwhich the rotor facing portion includes a clutch plate, the transmissionbody has an armature body, and the clutch plate is attracted to therotor by power supply, and wherein: the shim adjusts an axial positionof the clutch plate.
 8. The power transmission device according to claim7, wherein: the power transmission device is an electromagnetic clutchincluding an electromagnetic solenoid disposed within said rotor,wherein: the first rotation member of said clutch mechanism includes: anarmature for receiving the rotational force of said rotor when theelectromagnetic solenoid is in an operating state and the armature isattracted to said rotor; and a spring element for urging the armature tosecure a gap between said rotor and the armature in the axial directionwhen the electromagnetic solenoid is in a resting state, and wherein:the shim determines a size of the gap.
 9. The power transmission deviceaccording to claim 7, wherein: the power transmission device is a torquelimiter for breaking transmission of the rotational force from saidrotor to the rotary shaft when the rotary shaft comes into a lockedstate, wherein: the first rotation member of said clutch mechanismincludes a spring element connected to the rotor, and wherein: the shimsecures a gap between said rotor and the spring element in the axialdirection.
 10. The power transmission device according to claim 7,wherein: said clutch mechanism further includes a fastening elementdisposed in either one of the second rotation member and said hub, and areceiving element disposed in the other of the second rotation memberand said hub, and receives the fastening element to couple the secondrotation member and said hub to each other, and wherein: the shim has abore into which the fastening element is inserted.
 11. The powertransmission device according to claim 10, wherein: the fasteningelement is any one of a bolt, a pin, and a protruding portion integrallyformed in one or the other of the second rotation member and said hub.